1. Field of the Invention
The present invention relates to a high frequency metal oxide semiconductor (MOS) transistor, a method of forming the same and a method of manufacturing a semiconductor device including the same. More particularly, the present invention relates to a high frequency lateral double-diffused (LD) MOS transistor, a method of forming the same, and a method of manufacturing a semiconductor device having the LDMOS transistor.
2. Description of the Related Art
Semiconductor transistors can generally be classified as a bipolar junction transistor (BJT) and a field effect transistor (FET) in accordance with the type of charge carrier thereof.
While both electrons and holes carry charge in the BJT, only one of electrons or holes carry the charge in the FET. That is, charge in the BJT is carried by electrons and holes regardless of a transistor type such as an NPN transistor and a PNP transistor. However, charge in an N-type FET is carried by electrons, and charge in a P-type FET is carried by holes. The MOS transistor is type of FET, and enjoys widespread use in semiconductor devices.
The LDMOS transistor is most widely adapted to a lateral power device, and is characterized as having a high-input impedance and an expeditious response to a switching signal. The most important design factors of the LDMOS transistor are breakdown voltage and on-resistance. In particular, the breakdown voltage and the on-resistance greatly affect the performance of the LDMOS transistor when the LDMOS transistor is operated at a high frequency.
The breakdown voltage determines an operation voltage of a transistor. When a transistor operates as a rectifier and a switch at a high voltage, the breakdown voltage of a transistor is required to be high. In addition, when a transistor functions as a switch, an electrical resistance of a channel is required to be low in case the transistor is turned on (hereinafter, referred to as on-resistance of a transistor), and to be high in case the transistor is turned off (hereinafter, referred to as off-resistance of a transistor). In theory, the on-resistance of a transistor is to be zero, and the off-resistance of a transistor is to be infinite. However, in view of practical considerations, a transistor has a certain measurable amount of on-resistance and off-resistance, respectively. As a result, an excessively low off-resistance causes a leakage current, and an excessively high on-resistance leads to a fatal signal loss through a channel in real transistors.
Therefore, a transistor may be operated at a high voltage under the conditions of a high breakdown voltage and a low on-resistance. However, the breakdown voltage is generally incompatible with the on-resistance of a transistor. A high breakdown voltage necessarily causes a high on-resistance of a transistor, and a low on-resistance of a transistor necessarily requires a low breakdown voltage. When the breakdown voltage is low, a capacitance between a gate and a drain of a transistor is increased, so that an operation failure frequently occurs in a high frequency transistor.